Field of the Invention
This invention relates to a misfire detector for use in internal combustion engine which is based on the fact that an electrical resistant of the spark plug gap is distinguishable between the case when spark ignites air-fuel mixture gas, and the case when the spark fails to ignite the air-fuel mixture gas injected in a cylinder of the internal combustion engine.
With the demand of purifying emission gas and enhancing fuel efficiency of internal combustion engine, it has been necessary to detect firing condition in each cylinder of the internal combustion engine. In order to detect the firing condition in each of the cylinders, an optical sensor has been installed within the cylinders on one hand. Otherwise, a piezoelectrical sensor has been attached to a seat pad of the spark plug. Otherwise ion current flowing through an ignition circuit has been detected.
In either case, it is troublesome and time-consuming to install the sensor to each of the cylinders, thus increasing the installation cost, and at the same time, taking much time in check and maintenance.
Therefore, it is an object of the invention to provide a misfire detector for use in internal combustion engine which is capable of precisely detecting waveform of a secondary voltage applied to the spark plug installed to each cylinder of the internal combustion engine with a relatively simple structure.